Sidt2 is a key protein in the autophagy-lysosomal degradation pathway and is essential for the maintenance of kidney structure and filtration function.

The regulation and homeostasis of autophagy are essential for maintaining organ morphology and function. As a lysosomal membrane protein, the effect of Sidt2 on kidney structure and renal autophagy is still unknown. In this study, we found that the kidneys of Sidt2-/- mice showed changes in basement membrane thickening, foot process fusion, and mitochondrial swelling, suggesting that the structure of the kidney was damaged. Increased urine protein at 24 h indicated that the kidney function was also damaged. At the same time, the absence of Sidt2 caused a decrease in the number of acidic lysosomes, a decrease in acid hydrolase activity and expression in the lysosome, and an increase of pH in the lysosome, suggesting that lysosomal function was impaired after Sidt2 deletion. The accumulation of autophagolysosomes, increased LC3-II and P62 protein levels, and decreased P62 mRNA levels indicated that the absence of the Sidt2 gene caused abnormal autophagy pathway flow. Chloroquine experiment, immunofluorescence autophagosome, and lysosome fusion assay, and Ad-mcherry-GFP-LC3B further indicated that, after Sidt2 deletion, the production of autophagosomes did not increase, but the fusion of autophagosomes and lysosomes and the degradation of autophagolysosomes were impaired. When incubating Sidt2-/- cells with the autophagy activator rapamycin, we found that it could activate autophagy, which manifested as an increase in autophagosomes, but it could not improve autophagolysosome degradation. Meanwhile, it further illustrated that the Sidt2 gene plays an important role in the smooth progress of autophagolysosome processes. In summary, the absence of the Sidt2 gene caused impaired lysosome function and a decreased number of acidic lysosomes, leading to formation and degradation disorders of the autophagolysosomes, which eventually manifested as abnormal kidney structure and function. Sidt2 is essential in maintaining the normal function of the lysosomes and the physiological stability of the kidneys.

Transdermal delivery of triptolide-phospholipid complex to treat rheumatoid arthritis.

The aim of this study was to develop and evaluate a triptolide phospholipid complex (TPCX) for the treatment of rheumatoid arthritis (RA) by transdermal delivery. TPCX was prepared and characterized by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR) analysis, transmission electron microscope (TEM), and scanning electron microscope (SEM). The solubility of TPCX was determined. Then, a TPCX cream was prepared to evaluate its percutaneous permeability and the antiarthritis effect. The transdermal permeability was determined using the Franz method, and a microdialysis system was used for skin pharmacokinetic study. A rat model of RA was prepared to evaluate the pharmacological effects. TPCX increased the solubility of triptolide in water, and the percutaneous permeability of TPCX cream was greatly enhanced compared with triptolide cream. The skin pharmacokinetic study indicated that TPCX cream has a longer biological half-life (t1/2) and mean residence time (MRT), but it has a shorter Tmax than that of triptolide cream in vivo. The area under the curve (AUC0-t)/AUC0-∞) and the peak concentration (Cmax) of TPCX cream were obviously higher than those of triptolide cream. The TPCX-loaded cream alleviated paw swelling and slowed down the progression of arthritis by inhibiting the inflammatory response by down regulating the TNF-α, IL-1ß, and IL-6 levels, thus exhibiting excellent antiarthritic effects. In summary, the prepared TPCX effectively increases the hydrophilicity of triptolide, which is good for its percutaneous absorption and enhances its effect on RA rats. TPCX can be a good candidate for the transdermal delivery to treat RA.

The Effects of Sidt2 on the Inflammatory Pathway in Mouse Mesangial Cells.

In patients with chronic kidney disease, the abnormal activation of inflammatory pathways is usually an important factor leading to renal fibrosis and further deterioration of renal function. Finding effective intervention targets of the inflammatory signaling pathway is an important way to treat chronic kidney disease. As a newly discovered lysosomal membrane protein, the correlation between SID1 transmembrane family member 2 (Sidt2) and the inflammatory signaling pathway has not been reported. The aim of this study was to investigate the effect of Sidt2 on inflammation by inhibiting the expression of the Sidt2 gene in a mouse mesangial cell line mediated by a lentiviral CRISPR/Cas9 vector. Hematoxylin and eosin staining and microscopy found that the mesangial cells lost their normal morphology after inhibiting the expression of Sidt2, showing that the cell body became smaller, the edge between the cells was unclear, and part of the nucleus was pyknotic and fragmented, appearing blue-black. The expressions of IKK ß, p-IKK α/ß, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the NF-κB pathway of the Sidt2 -/- group were higher than those of the Sidt2 +/+ group. p-Jak2 and IL6 increased in the Jak/Stat pathway, and p-ERK and p-P38 increased in the MAPK pathway. The expressions of IKK ß, p-IKK α/ß, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the NF-κB pathway of the Sidt2 +/++LPS group were significantly higher than those in the Sidt2 +/+ group. The expressions of IKK ß, p-IKK α/ß, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the Sidt2 -/-+LPS group were higher than those in the Sidt2 -/- group. The expressions of p-IKK α/ß, NF-κB p65, p-NF-κB p65, p-IκBα, IκBα, and TNF-α in the Sidt2 -/-+LPS group were higher than those in the Sidt2 +/++LPS group. In the Jak/Stat pathway, the protein expressions of p-Jak2 and IL6 in the Sidt2 +/++LPS group were higher than those in the Sidt2 +/+ group. The expressions of p-Jak2 and IL6 in the Sidt2 -/-+LPS group were higher than those in the Sidt2 -/- group. The expressions of p-Jak2 and IL6 in the Sidt2 -/-+LPS group were higher than those in the Sidt2 +/++LPS group. The expressions of p-JNK, p-ERK, p-P38, and ERK in the MAPK pathway in the Sidt2 +/++LPS group were higher than those in the Sidt2 +/+ group. The expressions of p-JNK, p-ERK, p-P38, and ERK in the Sidt2 -/-+LPS group were higher than those in the Sidt2 -/- group. The expressions of p-JNK, p-ERK, p-P38, and ERK in the Sidt2 -/-+LPS group were higher than those in the Sidt2 +/++LPS group. These data suggested that deletion of the Sidt2 gene changed the three inflammatory signal pathways, eventually leading to the damage of glomerular mesangial cells in mice.